Brain edema, by definition, is an increase in tissue water which for vasogenic, interstitial or late ischemic brain edema results in an increase of extracellular fluid volume. The objective of the proposed research is to learn how the tissue responds mechanically to the excess water and to what extend biomechanical factors influence the formation, spread, and resolution of edema. These factors are complex and interactive; however, it is possible to isolate these mechanisms by use of infusion edema model where spatial distribution, total edema value, rate of edema formation and chemical composition of the edema can be controlled. We plan to study the dynamics of edema resolution by introducing fluids of known volume and protein content into the brain and describe the time course of fluid clearance in early and late stages of resolution process. Additional viscoelastic studies describing mechanical alterations of brain tissue passively involved in bulk flow will be conducted to identify areas of brain selectively vulnerable to distortion under normal pressure conditions. The pressure effects of the edema and the attendant changes in tissue properties will be characterized to test the proposed therapeutic maneuver of lowering intracranial pressure to enhance fluid clearance. Knowledge of brain edema dynamics should suggest new approaches to therapy.